# RPM packaging: adding a sub package to an already existing package (RHEL & centos)

In this document we will follow an example where existing package is ignition
(https://gitlab.com/redhat/centos-stream/rpms/ignition) and we want to add fedora-iot/ignition-edge
(https://github.com/fedora-iot/ignition-edge) as a sub-package .

- Fork https://gitlab.com/redhat/centos-stream/rpms/ignition this repo with your gitlab account.
- Clone the forked repository of the package to which you intend to add a sub-package.

git clone [e-mail]:<your-git-username>/ignition.git 
cd ignition

- At minimal a package will have .spec file, which basically holds steps for packaging.
Now we need to make changes in the .spec file.
- Refer https://rpm-packaging-guide.github.io/#working-with-spec-files to get better understanding
of spec files.
- In order to add a sub-package we need to mention source of the sub-package as follows

%global ignedgecommit a3a8f0abb2a1c7fc1c9e5d0e7a3e8830b2e2d766
%global ignedgeshortcommit %(c=%{ignedgecommit}; echo ${c:0:7})

Source1: https://github.com/fedora-iot/ignition-edge/archive/%{ignedgecommit}/ignition-edge-%{ignedgeshortcommit}.tar.gz

- In above code `ignedgecommit` and `ignedgeshortcommit` are nothing but two macros which
hold commit id of the latest commit of ignition-edge sub-package.
- Update the release version accordingly.

- Add necessary info about the sub-package:

############## ignition-edge sub-package ##############

%if 0%{?rhel} && !0%{?eln}
%package edge

Summary: Enablement glue for Ignition on ostree systems
License: ASL 2.0

%description edge
This package contains dracut modules, services and binaries needed to enable
Ignition on ostree systems.
%endif

- Add following under `%prep` section

tar xvf %{SOURCE1}

- Add following under `%install` section 

%if 0%{?rhel} && !0%{?eln}
%make_install -C ignition-edge-%{ignedgecommit}
%endif

- Add all the required modules and services under `%files` section 
- For example in this case 

%if 0%{?rhel} && !0%{?eln}
%files edge
%license %{golicenses}
%doc %{godocs}
%{dracutlibdir}/modules.d/35ignition-edge/*
%{dracutlibdir}/modules.d/10coreos-sysctl/*
%{dracutlibdir}/modules.d/99emergency-shell-setup/*
%{dracutlibdir}/modules.d/99journal-conf/*
%{_unitdir}/coreos-check-ssh-keys.service
%{_unitdir}/coreos-ignition-write-issues.service
%{_unitdir}/ignition-firstboot-complete.service
%{_libexecdir}/coreos-ignition-write-issues
%{_libexecdir}/coreos-check-ssh-keys
%endif

- Add relative information about your change under `%changelog` section.
- Once done with changes in .spec file, generate `sources` file by uploading the the 
 sub-package (ignition-edge) to the build system.
- We need `centpkg` utility for this. For Fedora, install with `dnf install centpkg` 
 command . OR follow instructions under https://copr.fedorainfracloud.org/coprs/james/centpkg/.
- Before that make sure you have krb5 tickets generated for your system. Following command fkinit generates the tickets for specified username.

sudo dnf install fedora-packager fedora-review
sudo usermod -a -G mock <username>
fkinit -u <username>

- Also generate/update ca-certificate to avoid SSL certificate error

sudo wget https://password.corp.redhat.com/RH-IT-Root-CA.crt -O /etc/pki/ca-trust/source/anchors/Red_Hat_IT_Root_CA.crt --no-check-certificate

sudo wget https://password.corp.redhat.com/pki-ca-chain.crt -O /etc/pki/ca-trust/source/anchors/PKI_CA_Chain.crt --no-check-certificate

ln -sf /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem /etc/pki/tls/certs/ca-bundle.crt

sudo update-ca-trust

- Download the ignition-edge-a3a8f0a.tar.gz subpackage locally.

curl -O https://github.com/fedora-iot/ignition-edge/archive/a3a8f0abb2a1c7fc1c9e5d0e7a3e8830b2e2d766/ignition-edge-a3a8f0a.tar.gz

- Upload the source of sub-package

centpkg upload ignition-edge-a3a8f0a.tar.gz

- Verify if that adds SHA512 hash of the source in `sources` file

cat sources
SHA512 (ignition-2.14.0.tar.gz) = e66d42bcfc516055f61abd1808e7ed1bdb4bf4e99b69c16ab9031be173a709c5864e74f23033cb33288e758b2f98a1dd878ef1aa802220afa504997fc3440af3
SHA512 (ignition-edge-a3a8f0a.tar.gz) = cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce47d0d13c5d85f2b0ff8318d2877eec2f63b931bd47417a81a538327af927da3e

- So in the above file, ignition-2.14.0.tar.gz is the main package and we have added 
 ignition-edge-a3a8f0a.tar.gz this as a sub-package successfully.

- Create a merge request from your forked repo and once this change is approved and 
 merged, latest package will be made available for centos and rhel.


## Refer
Please refer https://rpm-packaging-guide.github.io/ this documentation for understanding
more about rpm packaging.